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GEM1 Hazard: Description of Input Models, Calculation Engine and Main Results

M. Pagani, D. Monelli, H. Crowley, L. Danciu, E. H. Field, S. Wiemer, D. Giardini




This document provides an overview of the PSHA input models collected during GEM1, of the engine used to perform PSHA calculations, and the methods and criteria adopted for computing a proof-of-concept global hazard map. The GEM1 PSHA input repository contains seventeen national or regional models and one global model based on a smoothed seismicity approach. The oldest models were developed in the context of the GSHAP project, ended at the end of the 1990s; the most recent models are the ones prepared by the USGS-NSHM project for South America and a global smoothed seismicity model specifically produced for GEM1. In terms of geographical coverage the gathered models cover almost all the globe; the only missing regions are the Caribbean, the area around Papua-New Guinea and the Pacific Islands. These areas will hopefully be updated soon in the context of Regional Initiatives. In terms of information content, a relevant part of the PSHA input models is based on area sources while a minority uses fault sources. All the models but the Japanese and the model for the New Madrid Zone in the eastern US incorporate a time independent Poissonian model. Least but not last, epistemic uncertainties are taken into account by just some models, usually the most recent ones, and frequently treated as aleatory in the calculations.

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